FILE - A Saturday, Jan. 15, 2011 file photo, shows Iran's heavy water nuclear facilities near the central city of Arak 150 miles (250 kilometers) southwest of Tehran. Iran has floated specific dates for reopening talks with the U.S. and other world powers about its nuclear program. At the same time, Tehran has left U.N. nuclear inspectors empty-handed when it comes to addressing Western suspicions that it's conducting tests related to nuclear weapons. (AP Photo/ISNA,Hamid Foroutan, File)

Photo: Hamid Foroutan, Associated Press

FILE - A Saturday, Jan. 15, 2011 file photo, shows Iran's heavy...

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FILE - In this Saturday, Feb. 3, 2007 file photo, an Iranian technician works at the uranium conversion facility just outside the city of Isfahan 255 miles (410 kilometers) south of the capital Tehran, Iran. Iran has floated specific dates for reopening talks with the U.S. and other world powers about its nuclear program. At the same time, Tehran has left U.N. nuclear inspectors empty-handed when it comes to addressing Western suspicions that it's conducting tests related to nuclear weapons. (AP Photo/Vahid Salemi, File)

In a defiant move ahead of nuclear talks, Iran has announced plans to vastly increase its pace of uranium enrichment, which can make both reactor fuel and the fissile core of warheads. Eager to avoid scuttling those negotiations, world powers are keeping their response low-key.

The brief note quoted Iran as saying new-generation IR2m "centrifuge machines ... will be used" to populate a new "unit" - a technical term for an assembly that can consist of as many as 3,132 centrifuges.

A senior diplomat said it would take weeks, if not months, to have the new machines running once technicians started putting them in.

Mark Fitzpatrick, a nonproliferation expert and former senior official at the U.S. State Department, described the planned upgrade as a potential "game-changer."

"The timeline for being able to produce a weapon's worth of fissile material will significantly shorten," said Fitzpatrick.

Iran insists it does not want nuclear arms and argues it has a right to enrich uranium for a civilian nuclear power program.